Coal ash has caused some major environmental disasters in the United States, including a 2008 spill of more than 1 billion gallons of coal ash water into Tennessee’s Emory River and a 2014 spill into the Dan River, which flows through North Carolina and Virginia.
An industry group is promoting recycling as part of the solution to dealing with coal ash, the noncombustible by-products left over from burning coal for electricity, although environmental groups are urging caution.
“When you think of the total [amount of] coal ash produced every year, it’s the second-largest waste stream in the country. Municipal solid waste—household trash—is the largest,” said Thomas Adams, executive director of the American Coal Ash Association (ACAA), at a 21 November news briefing by the group in Washington, D. C.
Recycling of coal ash increased in percentage in the United States to 56% in 2016, up from 52% the previous year, ACAA announced at the event. “From an environmental standpoint, there’s a benefit of not sending material to disposal,” Adams said.
ACAA, which has tracked coal ash recycling since 1968, defines a use of coal ash as beneficial when it is environmentally responsible and sustainable, technically sound, and commercially competitive, noted Adams. “We’re really bringing a product to the market that is in demand and performs while we are helping the environment,” he told Eos. He said that recycling avoids some greenhouse gas emissions. Using fly ash in concrete reduces the amount of manufactured cement that is needed, thus cutting more than 11 million tons of greenhouse gases each year, according to ACAA.
Another benefit, said Adams, is reducing “situations where there is ash that is located in a place where there could be some danger of some kind of contamination,” such as near a river.
He said it could be possible to reclaim at least some ash currently in landfills and holding ponds. “We think there’s somewhere north of 2.5 billion tons in disposal” in the United States, he said. “If we could capture even 10%, it would be significant for not only beneficial use but certainly for the environment.”
Encapsulated Versus Unencapsulated
Coal ash encompasses several coal combustion residuals (CCRs), including fly ash, a lightweight material used in “encapsulated” or “bound” applications to improve the durability of concrete products, and bottom ash, used in “unencapsulated” or “unbound” applications in fill projects and for other purposes. The encapsulated use of CCRs binds coal ash, such as in concrete or wallboard, and minimizes residuals from escaping into the environment, according to the U.S. Environmental Protection Agency. Other CCRs include boiler slag, used as the gritty material on residential roof shingles, and synthetic gypsum, used in agriculture and construction, with about 50% of wallboard in the United States made with it.
ACAA numbers show that some encapsulated uses of coal ash declined in 2016, with coal ash in concrete down 8% and synthetic gypsum from the United States in wallboard down 19%. Meanwhile, much of the volume growth in recycling in 2016 came in categories such as “mining applications,” “structural fills/embankments,” and “waste stabilization,” according to ACAA.
Indeed, the volume of coal ash recycled overall has declined along with coal’s shrinking share of electricity generation, according to the most recent numbers. Last year, the amount recycled slipped to 60.2 million tons out of 107.4 million tons produced, which is down slightly from the 61.1 million tons recycled in 2015 out of the 117.3 million tons produced. ACAA released these figures at its November briefing.
To read the full story, visit https://eos.org/articles/group-touts-beneficial-coal-ash-recycling.